The changes in the demographic composition of the US workforce over the past several decades has been profound, with an ever increasing proportion of workers over the age of 50, but there has been inadequate attention to the occupational safety and health issues of these workers. How does the aging process affect risk for injury and musculo-skeletal disease? When injuries do occur in older workers, how do they compare in severity and cost to similar injuries in younger workers? Are there certain jobs or job characteristics which represent particular threats to aging workers, or others which are comparatively benign? In order to address these questions, the investigators have assembled a group of health, injury, administrative and environmental databases on the large and diverse US workforce of ALCOA, the world's leading aluminum manufacturer, for which the PI serves as medical director. Through multi-level analyses of these data, and collection of some additional data regarding work organization, we propose to: Aim 1: Determine the frequency of injury and MSD at the job specific level in older workers Aim 2: Determine the severity of injuries and MSD's for each job type in older workers Aim 3: Determine the characteristics at the job- level with higher and lower relative risks for older workers compared to younger workers Aim 4: Determine the potential modifying effects of demographic factors and health status on injury and MSD risk among older workers at the individual level. Aim 5: Determine the potential modifying effect of work organization and culture on risks for older workers at the location level. The results of these analyses will be used to develop strategies for subsequent intervention trials in this organization and industrial workforces generally.